This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Hey Richard, I'll stick my neck out - not that I am any authority at all on this = subject - but perhaps it will stir something up. I figure if I say = something outrageous enough, then someone that knows what they are = talking about will chime in. On a compression crowned soundboard, like a Steinway, the rib acts as = something to keep the one side of the panel from expanding when the = panel takes on moisture upon removal from the hot box - that is what = makes the panel crown. The ribs will be of constant thickness so that = the soundboard develops crown evenly. The ribs are thinned only at the = end to keep the soundboard flexible at the perimeter. A rib crowned soundboard will have ribs that are more evenly tapered = over most of their length, such as the taper you describe. That is = because such a shape better supports a load when applied to the middle = of the rib, such as downbearing on the bridge. That is what I think, but = you'd really need input from an engineer type to say more about that = subject. Now all other manufacturers use the Steinway-shaped rib because that is = what Steinway does. Is your soundboard crowned? Compression crowned? Rib crowned? Terry Farrell ----- Original Message -----=20 From: "Richard Brekne" <Richard.Brekne@grieg.uib.no> To: "Newtonburg" <pianotech@ptg.org> Sent: Friday, January 23, 2004 10:18 AM Subject: Rib Tapering > Ok soundboard makers of the nett... Question. >=20 > I have re-ribbed this old square grand soundboard, and used more or = less=20 > the ideas Joe and I exchanged, and I am ready to finish off the ribs=20 > now. On most of these oldies the ribs are very gradually thinned from=20 > the middle to the edges of the board. On newer instrument types the = ribs=20 > are the same thickness for most of the width of the panel, then = tapered=20 > suddenly. >=20 > So... what is the functional difference and what would be the=20 > recommended type of tapering for this case. It is a very low tension=20 > affair and probably will not be able to exert so very much down = bearing=20 > if that means anything. If I had to hazard a guess I'd wonder about = how=20 > tapering effects the flexibility at the edges. But thats just = guessing. >=20 > First time out with a soundboard rebuild.... finally have my = fingernails=20 > a bit dirty with this kind of work. So any good advice is muchly=20 > appreciated. The panel was dried for 2 weeks in my shop to the lowest = RH=20 > we get in these parts... roughly 26 %. The panel is about half the=20 > thickness of a modern panel, and the ribs in question are about 1 cm=20 > thickness, 2 cm wide, and 2 of them are 60 cm long the third about 45. = I=20 > can post a picture if that would be of help. >=20 > Thanks muchly >=20 > RicB >=20 > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives > ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/60/90/98/a2/attachment.htm ---------------------- multipart/alternative attachment--
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